1. Technical Field
The present invention relates to rustproofing compositions which are applied to parts for car bodies, parts with pockets or the like in vehicles, in particular in automobiles, and relates to rustproofing compositions which can be used for long-term rustproofing for common metallic materials.
2. Background Art
As a rustproofing agent for parts around tires, parts with pockets, and plate-bonded parts, a rustproofing agent in which wax and several kinds of additives are dissolved or dispersed in organic solvents such as mineral spirits, that is, wax-type rustproofing agents, have been used. Because these compositions exhibit high rustproofing ability, these compositions are also used as long-term rustproofing agents for metallic materials outdoors.
As a conventional wax-type rustproofing agent, for example, compositions with improved coating ability are disclosed in Japanese Unexamined Patent Application Publication No. 40159/85 or No. 92267/89, and a composition which improves production technology is disclosed in Japanese Unexamined Patent Application Publication No. 55198/86. However, in these compositions, organic solvents such as mineral spirits are used as solvents for dilution and dispersion. There are cases in which more than 70 mass % of such solvents is contained. Therefore, the organic solvent in the compositions evaporate into the air to form the wax coating which is a half-hard coating after the compositions are applied. Because such evaporated organic solvents are recently considered to be one of the causes of global warming, research to reduce organic solvents which are used in coatings is often performed and movements to regulate the amount of volatile organic solvent by law are increasing.
However, in the case in which organic solvents evaporated from the wax-type rustproofing agents are simply reduced, the viscosity of the agent is increased and sufficient permeation into gaps cannot be obtained. Therefore, 80 mass % of non-volatile content was a limit to maintain sufficient permeation in conventional technology. Furthermore, as a method to reduce organic solvents evaporated from the wax-type rustproofing agent, a method in which the organic solvent used in the compositions is substituted by high-viscosity oil having low volatility was examined. However, in this method, the coated film did not dry, the coated film flowed off under high temperatures or vibrations, the coated film was easily removed by a physical force such as contact with water or the like, and sufficient rustproofing ability could not be obtained.
In addition, as a method to reduce organic solvent, a method in which water-based rustproofing component is used was suggested. However, when the water-based rustproofing agents were applied to pockets in parts of car bodies or plate-bonded parts, water which was contained in the permeated compositions could not be evaporated and rust was generated. Furthermore, a rust preventing method in which a wax composition in a solid state at normal temperatures is heated to melt and is coated by dipping these parts into the melted wax, or a rust preventing method in which melted wax is used, was developed. However, such methods require large-scale equipment, and large amounts of heat are required to melt the solid wax, and these methods therefore have problems in cost efficiency.